Multimedia private branch exchanger and private branch exchange system

ABSTRACT

The router unit is built in the main key telephone apparatus, the office line interface function and the independent power supplying function are deleted in the router unit, and the office line interface units and the power supply unit substitute for these functions. The temperature inside the cabinet, the operated state of the cooling fan, and the temperature and operating power supply voltage Vcc of the PC power supply unit, etc. are detected in the CTI personal computer, and these monitor data are transferred to the main key telephone apparatus and analyzed in the main key telephone apparatus, so as to detect abnormality in the CTI personal computer and take necessary measures against the abnormality.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a private branch exchange systemsuch as a key telephone system, and particularly to a multimedia privatebranch exchanger capable of handling video signals, computer data andthe like as well as voice signals and a private branch exchange systememploying CTI (Computer Telephony Integration).

[0002] Many key telephone systems have been employed in office buildingsand company offices. Recently, as an extension-type system thereof, amultimedia-applicable key telephone system has been proposed, whichprocesses not only voice signals at telephone terminals, but also videosignals and computer data at videophone terminals and personalcomputers.

[0003] However, in a conventional system of this kind, for example, astandalone router is provided separately from a main key telephoneapparatus so that a data terminal connected to a LAN (Local AreaNetwork) is connected to the main key telephone apparatus via thestandalone router. Therefore, the standalone router and an interfaceunit dedicated for the main device need to be prepared for connection tothe LAN, which increases the user's economic burden.

[0004] On the other hand, employment of a CTI (Computer TelephonyIntegration) has been reviewed for constitution of the key telephonesystem. The CTI allows the main key telephone apparatus to be connectedto a server computer or personal computers, and the computers to processthe parts of the exchange of the main key telephone apparatus andstorage and working of the voices and data, etc. The CTI can realize ahigh-performance system without enhancing the processing performance ofthe main key telephone apparatus.

[0005] Generally, the main key telephone apparatus is designed with highreliability so as to be operated under the unmanned control for a longtime. However, since a cheap widely used computer such as a personalcomputer is used as the CTI computer of the key telephone system, it canbe well expected that the CTI computer may often lapse into anuncontrollable state such as malfunction, or abnormality may occur in anair-cooling fan, a hard disc, a power supply, etc. In these cases, if amaintenance person or an operator is stationed near the CTI computer, hecan immediately finish the malfunction program and restart the operationof the computer, or stop the CTI computer to disconnect it from the mainkey telephone apparatus. Generally, however, a maintenance person or anoperator is not stationed. If the CTI computer is abnormally operated,the processing ability of the system is not only lowered, but also theabnormality in the CTI computer influences the main key telephoneapparatus, which may cause the system down. Therefore, effectivemeasures against such operational abnormality have been expected.

[0006] The conventional multimedia-applicable key telephone systemdescribed above has a problem that the router dedicated foraccommodation of the LAN and the interface unit dedicated for the maindevice need to be installed and thereby the manufacturing cost of thesystem may be increased.

[0007] In addition, in a case where the router is a general dial-uprouter, there are problems that (1) a new ISDN line other than the mainkey telephone apparatus needs to be drawn or an ISDN extension lineinterface unit dedicated for the key telephone need to be prepared; and(2) when the battery at the power failure is backed up, anuninterruptible power supply UPS needs to be prepared to enhancereliability.

[0008] Further, when the CTI is carried out, there is also a problemthat solutions to the operational abnormality of the computer have notbeen established.

BRIEF SUMMARY OF THE INVENTION

[0009] The present invention has been accomplished by considering theabove-described circumstances, and its first object is to provide amultimedia private branch exchanger which can accommodate the LAN whilerestricting the manufacturing costs of the system as much as possible.

[0010] The second object of the present invention is to provide aprivate branch exchange system which can effectively respond toabnormality in operations of the CTI computer.

[0011] In order to achieve the first object, there is provided amultimedia private branch exchanger, comprising: a line interface unithaving a function of controlling communication with extension linetelephone terminals; a router unit having a function of controllingcommunication with data terminals to be connected to the local areanetwork; an office line interface unit provided commonly to the lineinterface unit and the router unit, and having a function of controllingcommunication with an external communication network; and a switchingunit for selectively connecting the line interface unit and the routerunit to the office line interface unit, on the basis of a request forsetting a call.

[0012] The present invention has also a characteristic of comprising apower supply unit provided commonly to the line interface unit, therouter unit, the office line interface unit and the switching unit, andsupplying the power necessary for their respective operations from thepower supply unit to each of the units.

[0013] That is, in the present invention, the router unit for connectionof the local area network is built in the exchanger, this router unithas the only interface function with the local area network, and theoffice line interface unit and the power supply unit which have beenprovided in the exchanger are used as the office line interface unit andthe power supply unit provided normally in a general dial-up router.

[0014] Therefore, according to the present invention, the standalonerouter or the general dial-up router does not need to be providedseparately from the exchanger. In addition, the router unit of thepresent invention is not only built in the exchanger, but also theoffice line interface function and the power supply unit which have beenprovided in the exchanger are commonly used as the office line interfaceunit and the power supply unit which are to be provided in the routerunit. As a result, a system which is of high reliability, acomparatively small size and low manufacturing costs, can be provided.

[0015] The present invention has also a characteristic of comprising, inthe router unit, a protocol converting unit for connecting the dataterminals directly connected to the LAN, to the office line interfacewithin the exchanger. In this structure, when a plurality of dataterminals are connected to the local area network, the entire datatransfer between the data terminals and the respective unit in theexchanger can be subjected to the interface process in the router unit.As a result, the function of the interface with the exchanger does notneed to be provided at each of the data terminals and thereby the burdenon the data terminal users can be reduced.

[0016] Further, the present invention has also a characteristic ofcomprising a hub in the router unit and connecting a plurality of localarea networks or data terminal devices via the hub.

[0017] On the other hand, in order to achieve the second objectdescribed above, there is provided a private branch exchange system,comprising an exchanger for accommodating a plurality of extension linesand at least one office line and having various functions concerningexchange between the extension lines or between the extension liens andthe office line; and a CTI computer for carrying out part of thefunctions of the exchanger, and the system comprises, in the CTIcomputer, means for monitoring abnormality in its own device, and meansfor informing the exchanger of abnormality monitor results obtained bythe abnormality monitoring means, and also comprises, in the exchanger,means for receiving the abnormality monitor results from the CTIcomputer, means for discriminating abnormality on the basis of theabnormality monitor results received by the abnormality receiving means,and abnormality response means for optionally disconnecting the CTIcomputer from its own device on the basis of discrimination results ofthe abnormality discriminating means.

[0018] The abnormality monitoring means monitors at least one ofabnormality in a temperature inside the CTI computer, abnormality in thepower supply, abnormality in operations of a cooling device andabnormality in operations of the computer.

[0019] Therefore, according to the present invention, when abnormal riseof the temperature, abnormality in the power supply, operationalabnormality in the cooler, or operational abnormality in operations ofthe program occurs in the CTI computer, results of the detection areinformed from the CTI computer to the exchanger. In response to thisinformation, the abnormal state is discriminated by the exchanger. Ifthere is a danger of malfunction in the CTI computer, the CTI computeris disconnected. As a result, the operational abnormality in the CTIcomputer does not influence the exchanger and thereby the system downcan be preliminarily prevented.

[0020] Moreover, the present invention has also a characteristic offurther comprising, in the CTI computer, means for monitoring recoveringconditions of its own device from the abnormality, and means forinforming the exchanger of the recovery results monitored by therecovery monitoring means; and further comprising, in the exchanger,means for receiving recovery monitor results from the CTI computer,means for discriminating recovering conditions on the basis of therecovery monitor results received by the recovery receiving means, andmeans for restoring the connection with the CTI computer on the basis ofthe discrimination results of the recovery discriminating means.

[0021] According to the present invention, when the CTI computer isrecovered from the operational abnormality, the connection between theexchanger and the CTI computer is automatically restored. Therefore, forexample, when the CTI computer, which is abnormally operatedtemporarily, returns to the normal condition, or when the CTI computerreturns to the normal condition after the parts of the CTI computer areexchanged, the connection between the exchanger and the CTI computer canbe restored without waiting for the restoring operation to be made by amaintenance person.

[0022] Furthermore, the present invention has also a characteristic ofallowing the exchanger to inquire the CTI computer about operatedconditions of the CTI computer; and compulsorily resetting the CTIcomputer when a predetermined response to the inquiry is not sent fromthe CTI computer to the exchanger, for example when no response orabnormal command is returned.

[0023] Therefore, even when the CTI computer cannot be restored by itsown self, for example, when there is malfunction in the program of theCTI computer, the CTI computer can be reset by the exchanger and theoperated state of the CTI computer can be restored to the normalcondition.

[0024] In addition, as described above, when the cooler is broken,abnormality occurs in the power supply, or there is malfunction in theprogram, in the CTI computer, the information indicative of the abnormalcondition may be transferred from the exchanger to the extension lineterminals or a relay station and, for example, the information may bedisplayed on a LCD or voice messages may be made so as to inform theuser or a relay station operator of the information. Thus, the user orthe relay station operator can immediately understand that there hasbeen operational abnormality or malfunction in the program, in the CTIcomputer, and can thereby quickly take measures such as the restoringoperations.

[0025] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0026] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate presently preferredembodiments of the invention, and together with the general descriptiongiven above and the detailed description of the preferred embodimentsgiven below, serve to explain the principles of the invention.

[0027]FIG. 1 is a circuit block diagram illustrating a first embodimentof a digital key telephone system according to the present invention;

[0028]FIG. 2 is a circuit block diagram illustrating the router unit 14Aof FIG. 1 in more detail;

[0029]FIGS. 3A and 3B show the conversion from IP data signal to PPPprotocol format;

[0030]FIG. 4 is a circuit block diagram illustrating essential units ofthe system shown in FIG. 1;

[0031]FIG. 5 is a circuit block diagram illustrating the structure of aCTI personal computer shown in FIG. 4;

[0032]FIG. 6 is a flow chart showing a process and contents ofdiscriminating PC abnormality and controlling the correspondence theretoby means of a controller of a main key telephone apparatus;

[0033]FIG. 7 is a circuit block diagram illustrating a second embodimentof the digital key telephone system according to the present invention;

[0034]FIG. 8 is a circuit block diagram illustrating a third embodimentof the digital key telephone system according to the present invention;

[0035]FIG. 9 is a block diagram illustrating essential units of a fourthembodiment of the digital key telephone system according to the presentinvention;

[0036]FIG. 10 is a block diagram illustrating essential units of a fifthembodiment of the digital key telephone system according to the presentinvention; and

[0037]FIG. 11 is a block diagram illustrating essential units of a sixthembodiment of the digital key telephone system according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0038] (First Embodiment)

[0039]FIG. 1 is a block diagram illustrating an embodiment of amultimedia key telephone system according to the present invention inwhich 1A represents a main key telephone apparatus at the core of thissystem.

[0040] The main key telephone apparatus 1A comprises plural kinds ofoffice line interface units (a basic rate interface: BRI, a primary rateinterface: PRI) 11 and 12, a line interface unit (a digital keytelephone unit/standard telephone unit: DKU/STU) 13, a time switch unit(TSW) 15, and a central control unit (CTU) 17. These are mutuallyconnected via a voice bus (pulse code modulation highway: PCMHW) 19 anda control bus (data highway: DHW) 20.

[0041] The office line interface unit (BRI) 11 is connected to an ISDNpublic network NW via a subscriber line ISL corresponding to the ISDNbasic interface, for example to control establishment of a call with theISDN public network NW on the basis of the basic interface. The officeline interface unit (PRI) 12 is connected to the ISDN public network NWvia a subscriber line ASL corresponding to an ISDN primary rateinterface, for example to control establishment of a call with the ISDNpublic network NW on the basis of the primary rate interface.

[0042] The line interface unit 13 accommodates a plurality of extensionlines EL1 to ELm, which are connected respectively to extension lineterminals T1 to Tm. Digital key telephones, analog telephones andfacsimile devices are, for example, used as the extension line terminalsT1 to Tm. The digital key telephone is connected to the DKU, and theanalog terminal such as the analog telephone or facsimile device isconnected to the STU. The DKU processes the transmission and receptionwith the digital key telephone and the transfer of a digital signal. TheSTU processes the transmission and reception with the analog terminaland the analog/digital conversion of the signal.

[0043] The time switch unit 15 switches the channels of the digitalsignal transmitted between the office line interface units 11 and 12,and the line interface unit 13 via the voice bus 19 in accordance withinstructions of the central control unit 17. 18 denotes a power supplyunit, which generates a desired DC power supply voltage Vcc on the basisof the commercial power supply output (AC100V) and supplies the DC powersupply voltage Vcc to all the circuit units in the device including arouter unit described later.

[0044] Incidentally, a router unit 14A and a computer-connectinginterface unit (PC I/F) 16A are built in the main key telephoneapparatus 1A of the first embodiment. The router unit 14A is constitutedby a LAN interface unit (LAN I/F) 141, a bus interface unit (bus I/F)142 including a protocol converting unit and a control unit (CONT) 143.That is, in the router unit 14A, ISDN interface functions and a powersupply unit of a generally used dial-up router are deleted and the busI/F 142 including the converting unit having a protocol convertingfunction to connect a LAN 2 directly to the voice bus 19 and the controlbus 20 inside the main key telephone apparatus 1A is provided.

[0045]FIG. 2 shows the router unit 14A of FIG. 1 in more detail.

[0046] This router unit 14A is a circuit on a single card board and canbe detached from the main key telephone apparatus 1A. The router card(i.e. the router unit) is constituted as explained below. Therefore, ifthe user does not need the router function of the main key telephoneapparatus 1A, he can detach the router card from the main key telephoneapparatus 1A and, instead, connect an extension line telephone interfacecard having an extension line circuit or a trunk card having a trunkcircuit.

[0047] The router unit 14A is constituted by the LAN interface unit (LANI/F) 141, the bus interface unit (bus I/F) 142 and the control unit 143as described above.

[0048] The LAN interface unit (LAN I/F) 141 includes a modular 141A formaking connection to an external LAN, transformers 141B for insulatingthe interior of the unit, an Ethernet repeater 141C serving as a hub forsplitting one port to four ports, and an Ethernet interface adapter 141Dfor processing Manchester code conversion and a differential output anda differential input of signals.

[0049] The control unit 143 includes a controller 143A, a flash memory(a program memory) 143B, and a data memory (DRAM) 143C. The controller143A processes various kinds of controls on the basis of programs storedin the program memory 143B, such as, for example, analysis of MACaddresses and IP addresses transmitted from the Ethernet interfaceadapter 143D.

[0050] In addition, the control unit 143 has a PPP (point to pointprotocol) connecting function, which allows data terminals PC1-PCnconnected to the LAN to be connected to the Internet IN and the intranetITN via the ISDN public network NW. The control unit 143, which also hasa routing table at the flash memory 143B, carries out the routingprocess of packets transmitted between the data terminals PC1-PCn andthe ISDN public network NW, by referring to the routing table.

[0051] The bus interface unit (bus I/F) 142 includes a TS rateconverting unit 142A, a time switch (TSW) 142B, a CLK circuit 142C forgenerating a clock signal for the TS rate converting unit 142A and thetime switch 142B, and a protocol converting unit 142D.

[0052] The time switch 142B is connected to a connector for connectingit to a PCM highway 19 of the main key telephone apparatus 1A, and theprotocol converting unit 142D is connected to a connector for connectingit to a data highway 20 of the main key telephone apparatus 18.

[0053] The time switch 142B and the TS rate converting unit 142A serveas a time slot assignor, which processes conversion between a protocolof an ISDN layer 3 to be generated in the control unit 142 and aprotocol of an extension line control interface layer 3 of the main keytelephone apparatus 1A, in order to transmit the data transmitted fromthe LAN via the ISDN.

[0054] Specifically, a protocol signal of the layer 3 to be transmittedfrom the controller 143A of the control unit 143 via the control serialbus and used for connection of the ISDN line conversion/I.430 line isconverted into the protocol of the internal control interface layer 3,and then transmitted in transmission format mode of the data highway 20.

[0055] Next, an operation of the router unit 14A will be described.

[0056] The IP data having the MAC header transmitted from the LAN isreceived by the LAN interface unit 141.

[0057] Specifically, the interior of the LAN interface unit 141 isinsulated by the transformer 141B, and the IP data is input to theEthernet repeater LSI 141C and then input to the controller 143A of thecontrol unit 143 via the Ethernet interface adapter LSI 141D.

[0058] In the controller 143A, after the IP data signal is convertedinto the PPP protocol format, it is transmitted to the TS rateconverting unit 142A of the bus I/F 142 with a B channel signal of theISDN via the communication serial bus. The conversion from IP datasignal to PPP protocal format is shown in FIGS. 3A and 3B. The IP datasignal is also transmitted to the protocol converting unit 142D of thebus I/F unit 142 with a D channel signal of the ISDN via thecommunication address bus corresponding to the ISDN line conversionI.430 protocol.

[0059] In the bus interface unit 142, the time slot conversion iscarried out by the TS rate converting unit 142A and the time switch(TSW) 142B, so that the B channel signal transmitted from the controller143A is input to a PCM highway's own time slot and the D channel signalfrom the protocol converting unit 142D is input to a data highway's owntime slot. The “own time slot” is a time slot determined on the basis ofa position where the router card is accommodated.

[0060] A CTI personal computer (CTI PC) 3A is connected to thecomputer-connecting interface unit 16A. The computer-connectinginterface unit 16A has a function of transferring a digital voice signalbetween the CTI personal computer 3A and the voice bus 19, and afunction of transferring a control command and the like between thecentral control unit 17 and the CTI personal computer 3A.

[0061]FIG. 4 is a schematic diagram illustrating the connection betweenthe CTI personal computer 3A and the main key telephone apparatus 1A.The CTI personal computer 3A comprises a PC control unit 31 having amicro-computer as a main controller, a plurality of PCM processing units321, 322, . . . , a key telephone connecting interface unit 33 and a PCpower supply unit 34. The PC control unit 31, PCM processing units 321,322, . . . , and key telephone connecting interface unit 33 areconnected via a PC voice bus 35 and a PC control bus 36.

[0062] The PCM processing units 321, 322, . . . execute variousprocesses necessary for the CTI, such as compression and encoding orextension and decoding of the digital voice signal transmitted from themain key telephone apparatus 1A, synthesis of the voice, detection of aDTMF signal, processing of a facsimile signal, processing of a modemsignal, and the like.

[0063] On the other hand, the PC control unit 31, the key telephoneconnecting interface unit 33 and the PC power supply unit 34 areconstituted as follows. FIG. 5 is a circuit block diagram illustratingtheir structures. A cabinet interior cooling fan monitoring unit 37 anda cabinet interior temperature sensor 38 are provided in the CTIpersonal computer 3A. The cabinet interior cooling fan monitoring unit37 monitors the operated state of a cooling fan and outputs themonitoring information. The cabinet interior temperature sensor 38outputs temperature detection information representing the temperatureinside the cabinet.

[0064] The PC power supply unit 34 comprises a regulation unit 341, anoutput monitoring unit 342, a temperature sensor 343 and an outputcontrol unit 344. The regulation unit 341 generates a desired operatingpower supply voltage Vcc on the basis of the commercial power supplyoutput and supplies it to each unit inside the CTI personal computer 3A.The output monitoring unit 342 monitors the value of the operating powersupply voltage Vcc and outputs the monitoring information. Thetemperature sensor 343 detects the temperature in the PC power supplyunit 34 and outputs the information about the detection of temperature.The output control unit 344 controls operations of the regulation unit341 in accordance with the instructions from the PC control unit 31described later.

[0065] The PC control unit 31 comprises a CPU 311, a chip set 312, a CPUtemperature sensor 313 and a CPU cooling fan monitoring unit 314. TheCPU 311, which totally controls the operations of the personal computer3A, executes transmission and reception of the control signal via thechip set 312. The CPU temperature sensor 313 monitors the temperature ofthe CPU and outputs the information about the detection. The CPU coolingfan monitoring unit 314 monitors the operated state of the CPU coolingfan and outputs the monitoring information.

[0066] The key telephone connecting interface unit 33 has a datatransmitting unit 332, a data receiving unit 333 and a control unit 334,and executes the transfer of a digital voice signal and the control datawith the computer connecting interface unit 16A of the main keytelephone apparatus 1A. In addition, a condition monitoring unit 331 isprovided in the key telephone connecting interface unit 33. Thecondition monitoring unit 331 takes and stores the monitoringinformation of the cabinet interior cooling fan monitoring unit 37, thetemperature detection information of the cabinet interior temperaturesensor 38, the monitoring information of the operating power supplyvoltage Vcc, the temperate detection information of the temperaturesensor 343 in the PC power supply unit 34, the temperate detectioninformation of the CPU temperature sensor 313 and the monitoringinformation of the CPU cooling fan monitoring unit 314. Every time arequest for transmission of the monitoring data comes from, for example,the main key telephone apparatus 1A, the latest monitoring informationis transmitted from the data transmitting unit 332 to the main keytelephone apparatus 1A as the condition monitoring data.

[0067] The central control unit 17 of the main key telephone apparatus1A has a function of discriminating abnormality in the CTI personalcomputer 3A, a function of displaying and controlling abnormality and afunction of responding to and controlling abnormality.

[0068] The abnormality discriminating function transmits a request fortransmission of the monitoring data to the CTI personal computer 3A at aconstant interval, and receives the condition monitoring data that istransmitted from the CTI personal computer 3A in response to therequest. Then, the function discriminates, on the basis of the receivedcondition monitoring data, whether there is abnormality of the powersupply voltage value Vcc or abnormality of the cooling fan, or whetheror not the temperature rises abnormally, in the CTI personal computer3A. If the various abnormalities are detected by this function, theabnormality displaying and controlling function transmits the displaydata representing the detected abnormal condition to a specific keytelephone or a relay station and allows the display data to bedisplayed.

[0069] If an order to stop the operation or an order to restart is inputfrom the specified key telephone as a result of detecting any one of theabnormality in the power supply voltage value Vcc, abnormality in thecooling fan and the abnormal temperature rise by the abnormalitydiscriminating function, the abnormality response and control functionexecutes any one of the following three operations: (1) to transmit anorder to the CTI personal computer 3A to stop its operations; (2) totransmit an order to the CTI personal computer 3A to restart itsoperations; and (3) to transmit an order to the output control unit 344to stop the output of the PC power supply unit 34 and stop theoperations of the CTI personal computer 3A.

[0070] The central control unit 17 of the main key telephone apparatus1A also has a function of monitoring and responding to the recover ofthe CTI personal computer 3A. This function periodically monitors theoperated state of the CTI personal computer 3A and discriminates whetheror not the operated state thereof is recovered, when the operations ofthe CTI personal computer 3A are stopped. If the function detects thatthe abnormality is recovered, it restarts the CTI process using thepersonal computer 3A.

[0071] Next, the operations of the system having the above structurewill be described.

[0072] First, a case where the data terminal connected to the LAN 2makes data communication in the Internet will be explained.

[0073] It is assumed now that, for example, a user may operate the dataterminal PC1 to make a data communication with a desired counterpart inthe Internet IN. The data terminal PC1 transmits a connect message tothe main key telephone apparatus 1A on the basis of the TCP/IP(transmission control protocol/internet protocol). This connect messageis received by the router unit 14A of the main key telephone apparatus1A via the LAN 2.

[0074] After receiving the connect message, the router unit 14A executesthe steps to set a communication connection based on the PPP connectionwith the counterpart terminal connected in the Internet IN. As for theconnection in the ISDN line, the steps of setting the communicationconnection are executed in the ISDN public network NW via the controlbus 20 and office line interface unit 11 in the main key telephoneapparatus 1A. That is, the office line interface unit 11 is usedoriginally to make connection between the extension line terminals T1-Tmof key telephones and the ISDN public network NW, but in the presentembodiment it is also used to make connection between the router unit14A and the ISDN public network NW. The connection steps concerning theInternet are executed with a provider (not shown) via the PCM bus 19 andoffice line interface unit 11 in the main key telephone apparatus 1A andthe ISDN public network NW.

[0075] In the above steps of setting the communication connection, therouter unit 14A transmits a connect message to the counterpart terminalin the Internet IN on the basis of the TCP/IP. In response to thetransmission of the connect message, the process of setting the TCP/IPconnection is executed between the originating data terminal PC1 and theInternet IN. With this process, the communication connection is setbetween the originating internal data terminal and the counterpartterminal in the Internet IN, and after this, the data communication inthe Internet IN can be made between the data terminal PC1 and thecounterpart terminal.

[0076] Next, the operations in the communication using the CTI personalcomputer 3A will be explained.

[0077] It is assumed now that, for example, the data communication maybe executed between the extension line terminal T1 and an office lineterminal connected to the ISDN public network NW. In this case, adigital voice signal transmitted from the extension line terminal T1 isreceived by the line interface unit 13, transferred to the computerconnecting interface unit 16A via the voice bus 19, an transmitted fromthe computer connecting interface unit 16A to the CTI personal computer3A. In this CTI personal computer 3A, the digital voice signal iscompressed and encoded. This encoded digital voice signal transmittedback from the CTI personal computer 3A to the computer connectinginterface unit 16A, transferred from the computer connecting interfaceunit 16A to the office line interface unit 11 via the voice bus 19, andthen transmitted to the office line terminal of the communicationcounterpart in the ISDN public network NW. The voice signal transmittedfrom the office line terminal is transferred to the extension lineterminal T1 in the path which is reverse to the above path.

[0078] Incidentally, in the system of the present embodiment, thefollowing discrimination of abnormality, and response and controlthereof are executed in CTI personal computer 3A during such executionof the CTI. FIG. 6 is a flow chart showing the steps and contents of thecontrol.

[0079] That is, in the CTI personal computer 3A, the temperature in thecabinet and the operated state of the cooling fan, the temperature ofthe PC power supply unit 34 and the operating power supply voltage Vcc,and the CPU temperature in the PC control unit 31 and the operated stateof the CPU cooling fan, are detected and collected in the conditionmonitoring unit 331 of the key telephone connecting interface unit 33.The collected monitoring data are stored in the condition monitoringunit 331.

[0080] The main key telephone apparatus 1A periodically generates arequest for transmission of the monitoring data at the central controlunit 17 and transmits the request from the computer connecting interfaceunit 16A to CTI personal computer 3A (step 4 a). When the requestreaches the CTI personal computer 3A of the key telephone connectinginterface unit 33, the CTI personal computer 3A reads and encodes thelatest one of the stored monitoring data, and transmits it to the mainkey telephone apparatus 1A.

[0081] After transmitting the request for transmission of the monitoringdata, the central control unit 17 of the main key telephone apparatus 1Amonitors the arrival of the monitoring data from the CTI personalcomputer 3A at step 4 b while monitoring the procedure of the time atstep 4 c. If the monitoring data reaches within a certain time aftertransmitting the request, the received monitoring data is analyzed atstep 4 d, and it is discriminated on the basis of the results ofanalysis whether or not abnormality occurs in the CTI personal computer3A, at step 4 e. If no abnormality occurs, the control is finished andreturns to step 4 a, and the above control of the discrimination ofabnormality is repeated.

[0082] On the other hand, it is assumed now that any abnormality mayoccur in the CTI personal computer 3A. In this case, the central controlunit 17 of the main key telephone apparatus 1A transmits abnormalitydisplay data to a specific extension line terminal (for example, Tm)which is a key telephone at step 4 f and allows the data to bedisplayed. The abnormality display data, which is edited on the basis ofthe monitoring data transmitted from the CTI personal computer 3A sothat the user can easily recognize the contents of the abnormality, isconstituted by, for example, a mark representing the kind of theabnormality and a brief explanation.

[0083] The abnormality display data may be displayed visually oroccurrence of the abnormality may be announced with a voice message bytaking advantage of a voice synthesizing means. The extension lineterminal Tm displaying the data may be a key telephone or a relaystation.

[0084] After transmitting the abnormality display data, the centralcontrol unit 17 of the main key telephone apparatus 1A transfers to step4 g and transmits an order to stop the operation to the CTI personalcomputer 3A so that the CTI process can be stopped.

[0085] On the other hand, for example, if the operating system or theprogram runs away in the CTI personal computer 3A, the CTI personalcomputer 3A does not transmit the monitoring data even when the main keytelephone apparatus 1A transmits the request for transmission of themonitoring data to the CTI personal computer 3A. In this case, aftertransmitting the request, the central control unit 17 of the main keytelephone apparatus 1A transfers from step 4 c to step 4 d after acertain time has passed, then discriminates that the malfunction of theoperating system or program has occurred from the fact that themonitoring data does not reach, and transmits the display datarepresenting the discrimination result to a specific extension lineterminal Tm and allows the data to be displayed.

[0086] When a certain time has passed after the display data to displaythe occurrence of abnormality is transmitted, the central control unit17 transmits an order of restart to the CTI personal computer 3A andallows the computer to be restarted. Thus, the CTI personal computer 3Areturns to the normal condition.

[0087] As described above, in the first embodiment, the router unit 14Ais built in the main key telephone apparatus 1A, the ISDN office lineinterface function and the independent power supply function are removedfrom the router unit 14A, and these functions are implemented by theoffice line interface units 11 and 12 and the power supply unit 18 thatare already provided in the main key telephone apparatus 1A. That is,the router unit 14A employs the existing office line interface units 11and 12 and the existing power supply unit 18.

[0088] Therefore, the LAN can be included in the key telephone systemwithout preparing the router separately. In addition, the main keytelephone apparatus 1A serving as a highly reliable multimediainformation communication system can be constituted with a comparativelysimple and small structure, not by simply providing the router insidethe main key telephone apparatus 1A, but by realizing the office lineinterface function and the power supply function of the functionsnecessary for the router by taking advantage of the office lineinterface units 11 and 12 and the power supply unit 18 that are alreadyprovided in the main key telephone apparatus 1A.

[0089] In addition, since the interface functions including the protocolconverting function to connect the router unit 14A directly to the voicebus 19 and the control bus 20 in the main key telephone apparatus 1A areprovided in the bus I/F unit 142 of the router unit 14A, the interfacefunctions between the main key telephone apparatus and the routerdevice, which have been required in the prior art, do not need to beprovided.

[0090] Moreover, in the first embodiment, abnormality in the CTIpersonal computer 3A is detected and necessary measures responding tothe abnormality are taken by detecting the temperature in the cabinetand the operated state of the cooling fan, the temperature of the PCpower supply unit 34 and the operating power supply voltage Vcc, and theCPU temperature in the PC control unit 31 and the operated state of theCPU cooling fan, in the CTI personal computer 3A, transferring thesemonitor data to the main key telephone apparatus 1A and analyzing them.

[0091] Therefore, as the CTI personal computer 3A, an expensive computersuch as a server or a factor computer which is designed with highreliability to prevent abnormality from influencing the entire branchexchange system is not required, and a cheap and generally used personalcomputer can be used.

[0092] In addition, the transfer of the monitor data from the CTIpersonal computer 3A to the main key telephone apparatus 1A is executedin response to the request for transmission from the main key telephoneapparatus 1A. If the main key telephone apparatus 1A cannot receive themonitor data even after a certain time has passed, the main keytelephone apparatus 1A discriminates that the malfunction of the programor the OS has occurred in the CTI personal computer 3A and causes theCTI personal computer 3A to be restarted. For this reason, the presenceof the malfunction in the CTI personal computer 3A can be discriminatedin the main key telephone apparatus 1A when the received monitor data isanalyzed, and therefore, the main key telephone apparatus 1A canimmediately respond to the malfunction in the CTI personal computer 3A.

[0093] Furthermore, when abnormality in the CTI personal computer 3A isdetected on the basis of the analysis of the monitor data, the main keytelephone apparatus 1A generates the display data representing thecontents of the abnormality, transmits it to a specific extension lineterminal Tm and allows the data to be displayed. As a result, forexample, the condition of the operational abnormality in the CTIpersonal computer 3A can be informed to a person who maintains and usesthe system and, therefore, a quick and certain response to theabnormality in the operations of the CTI personal computer 3A, such as amaintenance call and the like, can be made.

[0094] (Second Embodiment)

[0095] In the second embodiment of the present invention, the CTIpersonal computer is also connected to the router unit via the LAN whichis connected to the router unit, in the main key telephone apparatus, sothat the data transmitted from the CTI personal computer can becommunicated in the Internet.

[0096]FIG. 7 is a circuit block diagram illustrating a structure of thedigital key telephone system according to the second embodiment. In thisfigure, the same portions as those shown in FIG. 1 are indicated by thesame reference numerals and their detailed explanations are omitted.

[0097] In a computer connecting interface unit (PC I/F) 16B provided ina main key telephone apparatus 1B, an internal interface function oftransferring the data with other circuit units in the main key telephoneapparatus 1B, and a computer interface function of transmitting the datawith a CTI personal computer (CTI PC) 3B, are provided.

[0098] In this structure, for example, if a voice packet for theextension line terminal T1 reaches via the Internet IN and the ISDNpublic network NW, the voice packet is received by the office lineinterface unit 11, input to a router unit 14B via the voice bus 19,transmitted from the router unit 14B to the CTI personal computer 3B viathe LAN 2 and a cable 25, and stored in the CTI personal computer 3B as,for example, a voice mail.

[0099] When the voice packet is transmitted to the extension lineterminal T1, it is decoded at the CTI personal computer 3B, andtransmitted to the computer connecting interface unit 16B of the mainkey telephone apparatus 1B via a computer connecting interface 24. Thevoice packet is transmitted from the computer connecting interface unit16B to the line interface unit 13 via the voice bus 19 and the timeswitch 15, and then transmitted from this line interface unit 13 to thedestination extension line terminal T1.

[0100] In addition, when the voice data is transmitted from theextension line terminals T1-Tm to the Internet IN as an IP packet, it istransmitted to Internet IN in a course reverse to the above-describedone. That is, the voice data transmitted from the extension lineterminals is transferred from the computer connecting interface unit 16Bto the CTI personal computer 3B in which the voice data is encoded. Thevoice data is converted to a packet in the CTI personal computer 3B onthe basis of the TCP/IP, then transferred to the router unit 14B, andtransmitted from this router unit 14B to the ISDN public network NW viathe office line interface unit 11.

[0101] As described above, according to the second embodiment, the CTIpersonal computer 3B can be connected to the router unit 14B via theLAN2 and the LAN cable 25 and, as a result, an internet telephone or afacsimile communication via the Internet can be executed by using theextension line terminals T1-Tm. In addition, if any problem occurs inone of the courses, the CTI process can be continued by using anothercourse.

[0102] (Third Embodiment)

[0103] According to a third embodiment of the present invention, in adigital key telephone system which does not use the CTI personalcomputer, the PCM processing unit is provided in the main key telephoneapparatus 1C, the voice encoding and decoding are executed in the PCMprocessing unit instead of the CTI personal computer, and the LANinterface function is provided in the PCM processing unit, so that thePCM processing unit can be connected to a router unit 14C via aninternal LAN cable 21 by this function.

[0104]FIG. 8 is a circuit block diagram illustrating a digital keytelephone system according to the third embodiment of the presentinvention. In this figure, the same portions as those of FIGS. 1 and 4are indicated by the same reference numerals, and their detailedexplanations are omitted.

[0105] A hub 141C is built in a router unit 14C.

[0106] A PCM processing unit 22 is formed of, for example, a DSP(digital signal processor) board and has a telephony gateway functionincluding a PCM encoding function and a connection protocol function(H.322) to the LAN, and a facsimile service function including afacsimile modem function, a file converting function and a filemanagement function. The PCM processing unit 22 is connected to a routerunit 14C via an internal LAN cable 21 for 10BASE-T.

[0107] With this structure, the data, which is to be transmitted betweenthe extension line terminals T1 to Tm and the Internet IN is subjectedto the process relating to the working of the IP packet as well as theencoding and decoding processes in the PCM processing unit 22, istransmitted to the Internet IN via the router unit 14C and the officeline interface units 11 and 12.

[0108] Therefore, the internet telephones of the extension lineterminals T1 to Tm and the facsimile communication using the Internet INcan be made in the completely similar manner to that of the secondembodiment, without connection to the CTI personal computer.

[0109] (Fourth Embodiment)

[0110] In the CTI personal computer, according to a fourth embodiment ofthe present invention, the condition monitoring unit which is providedin the key telephone connecting interface of aforementioned embodimentsis provided independently as an RAS (reliability, availability andserviceability) function unit, so that the temperature inside the CTIpersonal computer and the operated condition of the cooling fan aremonitored by the RAS function unit and the monitor data is transferredfrom the key telephone connecting interface to the main key telephoneapparatus 1A.

[0111]FIG. 9 is a circuit block diagram illustrating the structure ofthe digital key telephone system according to the fourth embodiment ofthe present invention. In this figure, the same portions as those ofFIG. 4 are indicated by the same reference numerals, and their detailedexplanations are omitted.

[0112] An RAS function unit 39 is provided in a CTI personal computer3E, separately from a key telephone connecting interface unit 33E. TheRAS function unit 39, which corresponds to the condition monitoring unit331 in FIG. 5, takes and stores the monitoring information of thecabinet interior cooling fan monitoring unit 37, the temperaturedetection information of the cabinet interior temperature sensor 38, themonitoring information of the operating power supply voltage Vcc, thetemperate detection information of the temperature sensor 343 in the PCpower supply unit 34, the temperate detection information of the CPUtemperature sensor 313 and the monitoring information of the CPU coolingfan monitoring unit 314. The latest monitoring information is read justwhen a request for transmission of the monitoring data reaches from themain key telephone apparatus 1A, and is transferred to a key telephoneconnecting interface unit 33E as the condition monitoring data. The keytelephone connecting interface unit 33E transfers the conditionmonitoring data from the data transmitting unit 332 to the main keytelephone apparatus 1A.

[0113] With this structure, the physical data can be converted to thelogical data in the RAS designing unit, so that the amount of thetransmitting data can be reduced and burden on a transmission path andthe central control unit 17 can be reduced.

[0114] (Fifth Embodiment)

[0115] According to a fifth embodiment of the present invention, in amain key telephone apparatus 1E, the monitoring data analyzing anddiscriminating function which is provided in the central control unit ofaforementioned embodiments is provided independently as a PC conditionmonitoring unit 23, and the condition monitoring data reaching from theCTI personal computer 3A is analyzed by the PC condition monitoring unit23 so as to discriminate the presence of the operational abnormality.

[0116]FIG. 10 is a circuit block diagram illustrating a structure of themain key telephone apparatus 1E according to the fifth embodiment of thepresent invention. In this figure, the same portions as those of FIG. 4are indicated by the same reference numerals, and their detailedexplanations are omitted.

[0117] The PC condition monitoring unit 23 is provided independently ofa central control unit 17E, in the main key telephone apparatus 1E. Thecondition monitoring data transferred from the CTI personal computer 3Ais received by a computer connecting interface unit 16E and then inputto the PC condition monitoring unit 23. The PC condition monitoring unit23 analyzes the condition monitoring data and discriminates whether ornot the cooling fan of the CTI personal computer 3A is stopped, thetemperature rises abnormality, or abnormality occurs in the operationalpower supply voltage Vcc. The results of the discrimination are input tothe central control unit 17E.

[0118] If the PC condition monitoring unit 23 detects the abnormality,the central control unit 17E generates data representing the contents ofthe abnormality, transmits it to the specific extension line terminal Tmand allows it to be displayed. When a stop ordering command reaches fromthe specific extension line terminal Tm, the computer connectinginterface unit 16E transmits an operation stopping order to the CTIpersonal computer 3A in accordance with the command so that theoperations of the CTI personal computer 3A are stopped. If the commandof the operation stopping order does not reach in a certain time afterthe transmission of the display data, the central control unit 17Evoluntarily generates the operation stopping order, transmits it to theCTI personal computer 3A and allows the operation to be stopped.

[0119] With this structure, the PC condition monitoring unit 23 isprovided in the main key telephone apparatus 1E so that the monitoringdata can be analyzed and abnormality can be discriminated in themonitoring unit 23 and, therefore, the burden on the central controlunit 17E can be reduced.

[0120] (Sixth Embodiment)

[0121] According to the sixth embodiment, in a main key telephoneapparatus 1F, the monitor data analyzing and discriminating functionwhich is provided in the central control unit of aforementionedembodiments is provided independently as the PC condition monitoringunit 23, and the condition monitoring data reaching from the CTIpersonal computer 3A is analyzed by the PC condition monitoring unit 23to discriminate the presence of the operational abnormality. Further, ifthe abnormality in the operation of the branch exchanger is detected,the computer is set in a waiting state until the initialization of theexchanger has been completed and the operated state of the exchanger isinitialized, and after the initialization has been finished, the waitingstate of the computer is released to restart the computer.

[0122]FIG. 11 is a circuit block diagram illustrating the structure ofthe main key telephone apparatus 1F according to the sixth embodiment ofthe digital key telephone system. In this figure, the same portions asthose of FIG. 10 are indicated by the same reference numerals, and theirdetailed explanations are omitted.

[0123] In the main key telephone apparatus 1F, a PC condition monitoringunit 23F is provided independently of a central control unit 17F. Thecondition monitor data transferred from the CTI personal computer 3A isreceived by a computer connecting interface unit 16F and then input tothe PC condition monitoring unit 23F. The PC condition monitoring unit23F analyzes the condition monitor data and discriminates whether or notthe cooling fan of the CTI personal computer 3A is stopped, thetemperature rises abnormality, or abnormality occurs in the operationalpower supply voltage Vcc. The results of the discrimination are input tothe central control unit 17F.

[0124] When the abnormality in the CTI personal computer 3A is detectedby the PC condition monitoring unit 23F, the central control unit 17Fgenerates the data representing the contents of the abnormality,transmits it to a specific extension line terminal Tm and allows it tobe displayed. When the stop order command reaches from the specificextension line terminal Tm, the computer connecting interface unit 16Ftransmits an order to stop the operation to the CTI personal computer 3Ain accordance with the command, so as to stop the operation of the CTIpersonal computer 3A. If the order command to stop the operation doesnot reach within a certain period after transmission of the displaydata, the central control unit 17F voluntarily generates the operationstop order, and transmits it to the CTI personal computer 3A to stop theoperation of the CTI personal computer 3A.

[0125] In addition, If the abnormality in the main key telephoneapparatus 1F is detected, the central control unit 17F generates thedata representing the contents of the abnormality, transmits it to aspecific extension line terminal Tm and allows it to be displayed. Then,the central control unit 17F inputs the reset condition information tothe PC condition monitoring unit 23F. In response to the reset conditioninformation, the PC condition monitoring unit 23F transmits a wait orderto the CTI personal computer 3A via the computer connecting interfaceunit 16F, and thereby sets the CTI personal computer 3A in a waitingstate. After this, the central control unit 17F initializes the operatedstate of the main key telephone apparatus 1F, and inputs the resetrelease information to the PC condition monitoring unit 23F after theinitialization has been finished. In response to the reset releaseinformation, the PC condition monitoring unit 23F transmits a releaseorder to the CTI personal computer 3A via the computer connectinginterface unit 16F, and thereby releases the waiting state of the CTIpersonal computer 3A. The central control unit 17F generates data oferasing the display of abnormality in the main key telephone apparatus1F, transmits it to a specific extension line terminal Tm, and therebyerases the display of abnormality.

[0126] With this structure, the burden on the central control unit 17Fcan be reduced, similarly to the fifth embodiment. In addition, evenwhen abnormality occurs in the main key telephone apparatus 1F, theoperation of the main key telephone apparatus 1F can be recoveredwithout giving bad influence to the operation of the CTI personalcomputer 3A.

[0127] (Other Embodiments)

[0128] The present invention is not limited to the above-describedembodiments. For example, the digital key telephone system has beenexplained in the embodiments. However, the present invention can beapplied to the digital private branch exchange system. In addition, thekind of the extension terminals, the structure of the main key telephoneapparatus, the structure of the router unit, the functions of thecentral control unit, the structure and connection of the CTI personalcomputer, and the like can be variously modified within a range whichdoes not exceed the inventive scope of the present invention.

[0129] As described above, in the present invention, the router unit forconnection of the local area network is built in the exchanger, thisrouter unit has the only interface function with the local area network,and the office line interface and the power supply unit which have beenprovided in the exchanger are used as the office line interface and thepower supply unit which are to be generally provided in the router.

[0130] Therefore, according to the present invention, the router unitdoes not need to be provided separately from the exchanger. In addition,the route unit of the present invention is not only built in theexchanger, but also the office line interface and the power supply unitwhich have been provided in the exchanger are used as the office lineinterface and the power supply unit which are to be provided in therouter unit. As a result, a system which is of high reliability, acomparatively small size and low manufacturing costs, can be provided.

[0131] According to the present invention of the other embodiments, whenthere is abnormality in the operations of the computer or malfunction inthe program, the conditions are discriminated by the exchanger todisconnect or reset the computer.

[0132] Therefore, the abnormality in the operations of the computer doesnot influence the exchanger and, as a result, the system down can bepreliminarily prevented and thereby the reliability of the system can beenhanced.

[0133] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

1. A multimedia private branch exchanger, comprising: a line interfaceunit for accommodating a plurality of extension lines and having afunction of controlling communication with telephone terminals to beconnected to said extension lines; a router unit for accommodating alocal area network and having a function of controlling communicationwith data terminals to be connected to said local area network; anoffice line interface unit being provided commonly to said lineinterface unit and said router unit, and having a function ofcontrolling communication with an external communication network; and aswitching unit for selectively connecting said line interface unit andsaid router unit to said office line interface unit, on the basis of arequest for setting a call.
 2. A multimedia private branch exchangeraccording to claim 1, further comprising a power supply unit providedcommonly to said line interface unit, said router unit, said office lineinterface unit and said switching unit, for supplying to each of saidunits power necessary for their respective operations.
 3. A multimediaprivate branch exchanger according to any one of claims 1 and 2, whereinsaid router unit comprises a protocol converting unit for connectingsaid data terminals directly to said office line interface unit.
 4. Amultimedia private branch exchanger according to claim 1, wherein a hubfor accommodating a plurality of local area networks or data terminaldevices is built in said router unit.
 5. A private branch exchangesystem, comprising an exchanger for accommodating a plurality ofextension lines and at least one office line and having variousfunctions concerning exchange between said extension lines or betweensaid extension liens and said office line; and a computer for carryingout part of the functions of said exchanger, wherein said computercomprises means for monitoring abnormality in its own device, and meansfor informing said exchanger of abnormality monitor results obtained bysaid abnormality monitoring means; and said exchanger comprises meansfor receiving the abnormality monitor results from said computer, meansfor discriminating abnormality on the basis of the abnormality monitorresults received by said abnormality receiving means, and abnormalityresponse means for optionally disconnecting said computer from its owndevice on the basis of discrimination results of said abnormalitydiscriminating means.
 6. A private branch exchange system according toclaim 5, wherein said abnormality response means comprises a function ofresetting or stopping said computer.
 7. A private branch exchange systemaccording to claim 5, wherein said abnormality monitoring means monitorsat least one of abnormality in a temperature inside said computer,abnormality in the power supply, abnormality in operations of a coolingdevice and abnormality in operations of said computer.
 8. A privatebranch exchange system according to claim 5, wherein said computerfurther comprises means for monitoring recovering conditions of its owndevice from the abnormality, and means for informing said exchanger ofthe recovery results monitored by said recovery monitoring means; andsaid exchanger further comprises means for receiving recovery monitorresults from said computer, means for discriminating recoveringconditions on the basis of the recovery monitor results received by saidrecovery receiving means, and means for restoring the connection withsaid computer on the basis of the discrimination results of saidrecovery discriminating means.
 9. A private branch exchange system,comprising an exchanger for accommodating a plurality of extension linesand at least one office line and having various functions concerningexchange between said extension lines or between said extension liensand said office line, and a computer for carrying out part of thefunctions of said exchanger, wherein said system further comprises:means for allowing said exchanger to inquire said computer aboutoperated conditions of said computer; and means for compulsorilyresetting said computer when a predetermined response to said inquiry isnot sent from said computer to said exchanger.
 10. A private branchexchange system according to claim 9, wherein said resetting meanscompulsorily resets said computer when said computer makes no responseto said inquiry.
 11. A private branch exchange system according to claim9, wherein said resetting means compulsorily resets said computer whensaid computer sends back abnormal data in response to said inquiry. 12.A private branch exchange system according to any one of claims 5, 8 and9, wherein said exchanger further comprises means, when abnormality inoperations of said computer is detected, for transmitting information ofthe abnormality to telephone terminals to be connected to said extensionlines to inform said telephone terminals of said information.
 13. Aprivate branch exchange system according to any one of claims 5, 8 and9, wherein said exchanger further comprises means, when a relay stationis connected to said exchanger and if abnormality in operations of saidcomputer is detected, for transmitting information of the abnormality tosaid relay station to inform said relay station of the abnormality. 14.A private branch exchange system, comprising an exchanger foraccommodating a plurality of extension lines and at least one officeline and having various functions concerning exchange between saidextension lines or between said extension liens and said office line,and a computer for carrying out part of the functions of said exchanger,wherein said system further comprises: means for monitoring theabnormality in operations of said exchanger; means for initializing anoperated state of said exchanger when the abnormality is detected in theoperations of said exchanger by said abnormality monitoring means; andmeans for setting said computer to be in a waiting state by the timewhen the initialization has been completed by said initializing means,releasing the waiting state of said computer after said initializationhas been finished and restarting said computer.